Referigerant Charging
2
Engineered Systems Group Product Service ESG Service Information New 02-03 Refrigerant Charging in OM Titan or Other Always Flooded Chillers File In/With: N/A SI0055 Equipment OM Titan Chillers Affected: General This letter establishes guidelines and procedures which a eld technician can use to attain a properly charged sys- tem at full load and design conditions, without causing overchar ging and the resultant added expense in materials, refrigerant, and labor. Use the following steps for charging procedures. 1. Charge the full estimated amount into a storage receiver , if available. a. Refer to Unit Arrangement drawings in the IOM under the S ystem Design tab for the estimated amount. Y ou’ll nd it listed unde r “ESTIMATED OPERA TING WEIGHTS”, or on the uni t “G & A” drawing. b. It’s best to begin with, and to maintain a known amount of refrigerant in the system so you always know where you are at during the charging procedure. Do this by weighing all refrigerant cylinders before and after installatio n of refrigerant into the sys tem and record the weights. c. Get and keep all relevant documentation and informatio n about the vendor deliv ered refrigerant. If the quality of the refrigerant is questioned, you’ll have a paper/info trail to the source, which may help diagnose the problem. d. Refrigerant testing all cylinders before charging into the system is probably too costly at every site. However, comparing the saturation pressure/temperature with the ambient temperature of each cylin- der is a simple process that can be a saver of time and money . Refrigerant vendors can make mis- takes. Refrigerant delivered v ia tanker , has a quality report associated with it. Secure a copy of i t. e. Be sure that all refrigerant transfer lines are clean and are evacuated/purged free of inerts. 2. Charge 80% to 90% of the refrigerant into the system using refrigerant either from the storage receiver , or directly from the transport cylinders if a storage receiver is not used. When charging, remember it's easier to add than take out refrigerant. 3. Run the system. a. Turn the liquid injection valve (sound suppression) off. b. Adjust the hot gas de-superheating valve (quench) and leave it at the adjusted position. c. Start with a small CHILLED WATER Delta T and decrease the outlet temperature setpoint slowly. This gives you enough control over the system operation to smoothly approach design outlet tem- perature and prevents creating an unstable conditio n which could cause the unit to shutdown. 4. Establish subcooler level. a. The design level of t he subcooler is 50% of the s ight glass. This level will physi cally be in between the top of the subcooler tube bundle and the deck separating the condenser and subcooler. b. Tune this level controller to a steady o peration. Remember, a change in refri gerant charge will hav e an effect on the subcooler level. Final tuning occurs at time of charge completion. 5. Operate the system at Full Load/ Design Operating Conditions.
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Transcript of Referigerant Charging
7/31/2019 Referigerant Charging
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SI0055
2 YORK INTERNATIONAL
a. Locate these conditions (pressure, temperature, ow…etc) on the Unit Arrangement drawings under
the info titled “DESIGN LOAD CONDITIONS”. Other operating parameter information is located
on the P&ID drawings of the compressor, gear & motor (if applicable), and turbine (if applicable).
b. As the system capacity increases, the resident charge amount may be low. This can show up as low
evaporator pressure. Add refrigerant until you can get to the design load conditions.
c. The system instrumentation must be credible. If any instrument is in question, calibrate and verify.
Bad data will confuse the system analysis.
d. Record operating parameters and evaluate them against the design parameters.
e. An elevated suction superheat is normally the result of low charge. Remember, with current tube
technology, superheat may not readily be evident.
f. Low or no suction superheat is not always a bad condition. Check for sufcient discharge superheat.
Compare the saturated temperature/ pressure with the running conditions. There should be a mini-
mum of 2º of superheat. If it exists then the compressor is not being ooded. If it doesn’t, then the
suction is too “wet”, and evaporator or intercooler level is too high. A whirling amount of liquid in
the suction line sight glass is not a denitive sign of ooding over. A test for this is to shine a ash-
light from one of the sight glasses through to the other while observing the interior of the suction line.
If you can see through to the other side and the light, excessive carry over is not happening. If the
path is blocked, a dangerous situation has occurred, which requires immediate corrective action.
g. Check the “small difference”. This is dened as the temperature difference between the OUTLET
chilled water and the converted from pressure, suction temperature. A unit with “enhanced tubes”
can see as low as a 1º Fahrenheit temperature difference (outlet CHW is higher of the two).
h. The evaporator tube bundle is designed to be covered with an ebbulating (rolling boil) refrigerant
level. There will be more activity on the chilled water inlet end. Be aware that oil in the refrigerant
charge can affect the appearance of the levels in the evaporator. The amount of oil contamination can
be determined with a refrigerant sample test.
